Make `ChainSelStarvation` carry an `Enclosed` #4944

Job	Run time
Build and test (8.10.7, default, all)	40m 40s
Build and test (9.6.6, default, all)	27m 37s
Build and test (9.10.1, default, all)	25m 59s
Run benchmarks	0s
Deploy documentation to GitHub Pages	0s
	1h 34m 16s

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